Governor Janet Napolitano visits the HiROC lobby in February 2006

My favorite part is when people have questions for us – even when I don’t know the answers. Because, honestly, that’s what science is – we don’t always have the answers, but that’s what makes it exciting! It’s also fun to find out which aspects of the mission inspire other people, and I get a different perspective on what they think is interesting (versus just what I think is interesting!). Some of the questions are really good, too! We were talking with some middle-school students from El Paso, Texas, and their questions were so astute. One girl asked, “Does Mars have plate tectonics?” Another good question was, “How do we know about the interior of Mars?” These are great questions, and HiRISE is helping scientists to answer these and other questions, along with data from many other instruments studying Mars.

In case you were curious about these particular questions, like these kids were, here are some short answers and references for more information:

• Does Mars have plate tectonics?

  It doesn’t now, but it might have in the past. The crust of Mars is thicker and stronger than that of Earth, so it’s more difficult to break it apart into plates and start subducting them below one another. However, there is some evidence that Mars may have had active plate tectonics early in its history. Maybe the presence of water in the crust weakened the rock enough to allow plate tectonics. HiRISE is investigating evidence of water in the Martian past, which may help illuminate this issue.

  For more reading:

  1. “Plate Tectonics . . . on Mars” Science News Magazine Volume 155, Number 18 (May 1, 1999) (article)
  2. Sleep, N.H. 1994. Martian plate tectonics. Journal of Geophysical Research 99, 5639. (scientific paper)
  3. Nimmo, F., Stevenson, D.J. 2000. Influence of early plate tectonics on the thermal evolution and magnetic field of Mars. Journal of Geophysical Research 105, 11969-11980. (scientific paper)
• How do we know about the interior of Mars?

  HiRISE and other cameras can only take pictures of the surface of Mars. So how do we know so much about what’s inside the planet? For example, we know that Mars has an upper crust, a mantle, and a dense core, like the Earth.

  One way to see beneath the surface is to use impact craters – they punch holes through the crust and expose deeper rocks. HiRISE has imaged a lot of craters! There is also an instrument on the MRO spacecraft with HiRISE called SHARAD, which uses radar to see buried layers of rock and ice. We know about the deeper interior of the planet from spacecraft that have been orbiting Mars for decades and measuring how gravity, heat flow, and the magnetic field vary over different areas. We can also measure the elevation of different features, and that tells us something about what’s underneath. For example, a tall mountain may have very deep roots that extend into the mantle. Scientists also make theoretical models of the planet based on what we know about the physics and chemistry of how it formed and has evolved. There is still a lot of work to be done in this area, and scientists hope future missions will tell us more about the Martian interior. For example, a seismic

  For more reading:

  1. “Martian Interior” (2007) European Space Agency. (article)
  2. Zuber, M.T. 2001. The crust and mantle of Mars. Nature 412, 220-227. (scientific paper)
  3. Planetary Interiors by W. Hubbard (book, general to all planets)

My presentation went well. For some reason I was especially nervous right before the talk, but immediately after I started my nervousness went away, most likely because my hosts and the audience were so receptive. I am not sure how many people attended, but the room was full. At the end of the presentation there were a lot of great questions from the audience, including basic questions about Mars, questions about our current understanding of Mars, questions about HiRISE and its capabilities, and questions about the future of space exploration. I put my foot in my mouth only once, when I referred to the Deep Space Network (DSN) as “antiquated”. A former JPL engineer in the audience politely and informatively corrected my word choice.

A couple weeks before the talk we snail mailed two color printouts of PSP_001336_1560 – “Delta in Eberswalde” – to Prescott for framing. One image is the entire black-and-white image with central color swath, and the other is a zoomed-in color subscene. During setup prior to the presentation, the frame shop delivered the images, and they had done a fantastic framing job! People were naturally drawn to the images before and after the presentation and I answered lots of questions about them.

I promised I would place the PowerPoint presentation online, and here it is. The PowerPoint presentation file is about 22 MB in size. I have notes in the notes section of the slides, including information about the images used as well as their URLs. I want to especially thank Stuart Heggie for allowing me to use his beautiful astrophotography image “Conjunction of Moon, Venus and Mars – Dec 1 2002“. His image helped me to make a point about the history of Mars observation.

Thank you to my hosts, including Meghan and Douglas, and everyone who attend a delicious pre-presentation pizza dinner, including the current and former presidents of the Prescott Astronomy Club and their spouses, the library’s Adult Services Director, and the talented graphic designer of many of their brochures and other materials (including a t-shirt I will take a picture of soon). The audience deserves my thanks because they had such great questions and were incredibly good-natured. Thank you, everyone!